So I finally put the top end of my engine back together (a '66 200 with a later model head) after pulling the head to get a crack in the intake manifold fixed. While the machine shop was fixing that they also milled it a bit (it had previously been milled as well). I had asked the machinist to try to get to 48cc's.
When I finally went to start it, it actually cranked over but it idled really poorly, so I ran a compression test and cylinders 1-4 and 6 were all 140-150... BUT cylinder 5 has zero compression. It doesn't even bump the gauge.
From what I've read, this seems to point to a valve stuck open since if the head gasket didn't seal properly it would most likely cause low compression in an adjacent cylinder too. Does that sound right? Anyone have any advice on how I could troubleshoot this a bit more before pulling the head again?
I took the valve cover off and when I crank it, both springs on that cylinder compress and pop back, but I'm not sure exactly what I'm looking for. Nothing stands out as looking really wrong compared to the other cylinders though.
I know some people have shimmed their rocker arms after milling, which I didn't do, but if the problem was that it's too close and not letting the valve come back up all the way, it would affect all of the valves not just for one cylinder right?
When I finally went to start it, it actually cranked over but it idled really poorly, so I ran a compression test and cylinders 1-4 and 6 were all 140-150... BUT cylinder 5 has zero compression. It doesn't even bump the gauge.
From what I've read, this seems to point to a valve stuck open since if the head gasket didn't seal properly it would most likely cause low compression in an adjacent cylinder too. Does that sound right? Anyone have any advice on how I could troubleshoot this a bit more before pulling the head again?
I took the valve cover off and when I crank it, both springs on that cylinder compress and pop back, but I'm not sure exactly what I'm looking for. Nothing stands out as looking really wrong compared to the other cylinders though.
I know some people have shimmed their rocker arms after milling, which I didn't do, but if the problem was that it's too close and not letting the valve come back up all the way, it would affect all of the valves not just for one cylinder right?